prova, here is a good introduction to the use of filters:-
http://sciastro.net/portia/advice/filters.htm
With respect to coloured filters or neutral density/polarising filters, there are people who reckon they are a great aid and others who find them little use. I have found coloured filters no benefit on Jupiter, but a younger viewer thought the yellow filter did help. I haven't tried them on much else as yet. I do, however, use a crossed polariser on the full moon in particular, even on Jupiter at one stage.
It would be best if you can try before you hand over big dollars. I guess $15 each for a few coloured filters isn't too much. However $59 for the polarising seems high (though the quality description is good). If you check around, you can get two 1.25" polarising filters for $25 that will achieve much the same result.
Also think about whether you will be wanting 2" filters for 2" eyepieces, rather than, or as well as 1.25" filters. A 2" filter can always be put onto the 1.25"-->2" adapter (watch the eyepiece doesn't hit the filter when inserted - tighten it up a bit higher if it looks like it will). Or it can be put on the end of a 2" barlow.
Eric
